If you don't care about overclocking, then the only question is your processor manufacturer and front side bus speed. Running memory beyond a 1:1 ratio (FSB clock : MEM clock)is all but worthless unless you're on an AMD system.
So, if you're on an AMD and want a ~5% (at best) boost in speed, get the 1066. For all current Intel systems or AMD system that isn't going to notice the tiny change, the DDR2-800 sticks will do exactly what you want.